Magnetic non-volatile memory element

ABSTRACT

A non-volatile magnetic memory device is proposed, which provides sufficient magnetic shielding performance for external magnetic fields. A first magnetic shield layer  60   a  and a second magnetic shield layer  60   b , both made of a soft magnetic metal, are formed respectively on the bottom surface of the transistor section  20 , which is the mounting side of the MRAM device  10 , and on the top surface of the bit line  50 , which is opposite to the bottom surface of the mounting side of the MRAM device  10 . On the second magnetic shield layer  60   a , a passivation film  70  is formed. The magnetic flux penetrated from the external magnetic field, is suppressed below the inversion strength of the MRAM device  10 , thereby improving reliability. Moreover, by using soft magnetic metal as the magnetic shield layers  60   a,    60   b , the magnetic shield layers can be formed by the sputtering technique, particularly composing elements can be partly shared as elements of the targets to be used for forming various layers composing the MRAM device  10  by the sputtering technique, thereby enabling to form various layers of the MRAM device  10  in a single sputtering chamber efficiently.

FIELD OF THE INVENTION

The present invention relates to a magnetic non-volatile memory device,more specifically to the one provided with a magnetic shield structurefor suppressing external magnetic field that may cause adverse effect oninformation stored therein.

BACKGROUND ART

Information communication equipment, especially compact personalequipment such as mobile terminals have become very popular and thisraises a strong need for higher performances such as higher integration,higher speed, lower power consumption, etc. of memories, logic devicesand the like to be used in such equipment. In particular, non-volatilememory devices are considered to be essential in the ubiquitous age. Incase of power shortage or a trouble of the equipment, or even in case ofinterruption of the connection due to a trouble between the server andthe network, the non-volatile memory devices are able to hold the storedinformation and thus protect important information.

Currently, flash memories using semiconductor, FRAMs (Ferro-electricRandom Access Memories) using ferro-electric material and the like arewidely used as such non-volatile memory devices. However, flash memorieshave a disadvantage in that the writing speed is in the order ofmicroseconds and thus very slow. On the other hand, FRAMs can berewritten in the range of 10¹²-10¹⁴, thereby making them impossible tocompletely replacing SRAMs (Static Random Access Memories) or DRAMs(Dynamic Random Access Memories) because of durability. Moreover,difficulty in microminiature processing of FRAMs is pointed out.

Incidentally, more recent portable equipment are designed to maintainnon-used circuit blocks in stand-by condition for reducing unnecessarypower consumption as small as possible. However, if a non-volatilememory having both functions of a high speed work memory and a largecapacity storage memory is achieved, it is possible to avoid waist ofpower and memories. It is also possible to realize so-called instant-onfunction in which the system can be started immediately after power-onif a high speed and large capacity non-volatile memories are available.

Non-volatile memories that may achieve the above objectives areattracting a great deal of attention and include, for example, amagnetic memory that is known as a MRAM (Magnetic Random Access Memory)(See Wang et. al., IEEE Trans. Magn. 33 (1997), 4498). The MRAM deviceis a semiconductor magnetic memory utilizing magneto resistance effectbased on the spin dependent conduction phenomenon that is peculiar to anano magnetic material and is a non-volatile memory capable of holdingstored information without externally supplying power.

Information writing in the MRAM device is carried out by combinedmagnetic fields of bit lines and word lines wired in matrix forinverting the magnetic spin of the cell at the cross point of the bitline and the word line, thereby recording the orientations as theinformation “1” or “0”. On the other hand, information reading iscarried out using the TMR (Tunnel Magneto Resistance) effect to whichthe magneto resistance effect is applied. The TMR effect is thephenomenon in which the resistance changes depending on the orientationof the spin. In case of reading the MRAM device, the information “1” or“0” is read out depending on whether the resistance is high or low.

Additionally, since the MRAM device has a simple construction, it iseasy to integrate. Also, since recording is made by rotating themagnetic moment, the number of rewritings can be very large. The accesstime is forecasted to be very high and is reported to be operable at 100MHz (See R. Scheuerlein et. al., ISSCC Digest of Technical Papers, pp.128-129, February 2000). As understood from the above, in conjunctionwith improved performance of the TMR materials in recent years, the MRAMdevices are attracting a great deal of attention and there are increasedhopes as high speed and large capacity non-volatile memories.

However, since the MRAM devices use a magnetic material for recordingand holding the information, there is a possibility that the recordedinformation is erased or rewritten by the influence of external magneticfields. Normally, the MRAM devices are mounted on a circuit board insidethe electronic machine or equipment. Depending on kinds of electronicmachine or equipment, as a progress of highly density mounting in recentyears, mounted densely on a circuit board are various devices such assemiconductor devices, communication devices, miniature motors and thelike other than the MRAM devices. Various mechanical componentsincluding an antenna, a power supply unit and the like are alsoinstalled inside the electronic machine or equipment to constitute asingle apparatus together with the circuit board having the MRAM devicesmounted thereon. This means that the MRAM devices are used in anenvironment of mixed magnetic fields over a wide frequency rangeincluding DC, low frequencies up to high frequencies. Accordingly, inorder to put the MRAM devices into practical use, the MRAM devices needto be improved in resistance to external magnetic fields by means ofimproved mounting and/or magnetic shielding of the MRAM devices, therebyenhancing reliability of holding the recorded information in suchdevices.

As examples of magnetic shielding of such MRAM devices, U.S. Pat. Nos.5,902,690 and 5,929,772 propose magnetic shielding structures for MRAMdevices. In particular, U.S. Pat. No. 5,902,690 proposes to provide theMRAM device with a magnetic shielding characteristic by using insulationferrite (MnZn and NiZn ferrites) layers that are soft magnetic metaloxides as a passivation film of the MRAM devices. On the other hand,U.S. Pat. No. 5,929,772 proposes to form a permalloy which is a magneticmember having a high magnetic permeability inside a package, therebypreventing magnetic flux from penetrating inside the device.

However, such conventionally proposed shield structure for MRAM devicesis not yet perfect and has a possibility to cause a problem bypermitting magnetic flux to penetrate into the MRAM devices and to erasethe stored information or overwrite.

In order to prevent magnetic flux from penetrating, it is necessary andthe most important to dispose a magnetic material having a highpermeability about the device, thereby providing a magnetic path so thatmagnetic flux does not penetrate into the device. In this point of view,the conventional methods to form a ferrite passivation film or forming apermalloy inside the package provide an incomplete magnetic shieldstructure because the magnetic path is not completely closed.

Moreover, in case of using a ferrite layer as the passivation film thatis made by a film forming by the sputtering technique, since the ferriteis an oxide magnetic material, it is most likely to cause oxygen loss,thereby making it very difficult to use a complete ferrite layer as thepassivation film. On the other hand, if the ferrite layer is formed byany technique other than sputtering, there encountered other problemssuch as increased manufacturing steps and cost in addition to decreasedproduction yield.

Furthermore, in case of disposing permalloys at both top and bottomlocations within the package, it is possible to obtain better shieldingperformance than the ferrite passivation film. However, since there isno magnetic interconnection between the top and bottom permalloys, themagnetic path is not established. Although this technique is effectivein high frequencies, a large effectiveness is not expected for lowfrequency magnetic fields that are common to the MRAM devices. Even ifone of the top and bottom permalloys is jointed to a ground layer of thedevice using an electrically conductive adhesive, the above mentioneddrawback of not establishing the magnetic path is still applicable,thereby not providing significant magnetic shielding.

The present invention is made in consideration of the abovecircumstances and it is an object of the present invention to provide anon-volatile magnetic memory device that provides sufficient magneticshielding performance for external magnetic fields over a wide frequencyrange.

DISCLOSURE OF THE INVENTION

The present invention is an MRAM device provided with a magneticshielding structure for suppressing the influence of external magneticfields characterized in that a magnetic shield layer is made from a softmagnetic metal on the surface of the device for suppressing penetrationof magnetic flux into the device.

According to the above construction, since the magnetic shield layer isformed on the surface of the MRAM device, penetration of magnetic fluxinto the MRAM device is suppressed. Furthermore, since a soft magneticmetal is used for forming the magnetic shield layer, it provides notonly the magnetic shield layer of higher permeability as compared to onemade from a soft magnetic metal oxide such as ferrite but also enablingto form the magnetic shield layer by the sputtering technique.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified drawing to show an exemplified construction ofthe MRAM device provided with a magnetic shielding structure accordingto the present invention.

FIG. 2 is a graph to show the relationship between the film thickness ofthe magnetic shield layer and the strength of the internal magneticfield.

FIG. 3 is a simplified drawing of the exemplified MRAM device formagnetically coupling the magnetic shield layer.

FIG. 4 is a simplified drawing of another example of the MRAM device formagnetically coupling the magnetic shield layer.

THE BEST MODE FOR CARRYIG OUT THE INVENTION

Now, embodiments of the present invention will be described hereunder byreference to the accompanying drawings.

FIG. 1 is a simplified drawing of an exemplified MRAM device providedwith the magnetic shield layer.

The MRAM device 10 is formed with a TMR section 40 for storing andholding information at a transistor section 20 which is formed forswitching by way of a word line 30 made from aluminum or the like and abit line 50 made from aluminum or the like is also formed on the TMRdevice section 40. Moreover, a first magnetic shield layer 60 a and asecond magnetic shield layer 60 b are formed respectively on the bottomsurface of the transistor section 20 and on the top surface of the bitline 50 for suppressing penetration of magnetic flux from externalmagnetic fields.

In order to protect the MRAM device 10, a passivation film 70 made fromsilicon nitride (SiN) or the like is formed on the second magneticshield layer 60 b which is formed on the bit line 50 defining a devicesurface opposite to the bottom surface of the transistor section 20which is a device surface at the mounting side of the MRAM device 10.

The transistor section 20 of the MRAM device 10 comprises the gate 22formed on a silicon substrate 21 and the source 23 and the drain 24formed on the silicon substrate 21. The gate 22 of the transistorsection 20 is connected to the word line 30 of the MRAM device 10.

The TMR device section 40 can be roughly divided into a fixed layer 41,an insulation layer 42, a recording layer 43 and a barrier layer 44. Thefixed layer 41 of the TMR device section 41 comprises a sequentiallamination of a PtMn layer 41 a of 300 Å in film thickness, an FeColayer 41 b of 30 Å in film thickness, a Ru layer of 8 Å in filmthickness, an FeCo layer 41 d of 20 Å in film thickness. The insulationlayer 42 is an Al₂O₃ layer of 15 Å in film thickness, the recordinglayer 43 is an FeCo layer of 30 Å in film thickness, the barrier layer44 is a Ta layer of 50 Å in film thickness. Among these layers, thebarrier layer 44 is connected to the bit line 50.

The first and second magnetic shield layers 60 a, 60 b are soft magneticlayers formed of a soft magnetic metal of the nano granular structure toachieve higher permeability or soft magnetic layers of a highpermeability soft magnetic metal. The first magnetic shield layer 60 ais formed on the bottom surface of the silicon substrate 21, while thesecond magnetic shield layer 60 b is formed on the top surface of thebit line 50,

Although not shown in the drawing, it is possible to provide a separatebarrier layer of the same material as the second magnetic shield layer60 b between the second magnetic shield layer 60 ba and the bit line 50.For example, if the second magnetic shield layer 60 b is made from anelectrically conductive material, an Al₂O₃ layer or the like may beformed as the barrier layer. This construction insulates between thesecond magnetic shield layer 60 b and the bit line 50, thereby improvingreliability of the MRAM device 10. In case of forming such barrierlayer, appropriate materials are chosen by considering variouscharacteristics and relationship of the second magnetic shield layer 60b, the bit line 50 and the barrier layer to be formed such as thecoefficient of thermal expansion other than the electrical conductivity.

In case of magnetic flux of external magnetic fields attempting topenetrate into the MRAM device 10 of the above construction, suchmagnetic flux is most likely to penetrate into the first and the secondmagnetic shield layers 60 a, 60 b among elements constituting the MRAMdevice 10. This is because the first and the second magnetic shieldlayers 60 a, 60 b are made from soft magnetic material having highpermeability, thereby enhancing the tendency of passing magnetic fluxthrough them. Moreover, once magnetic flux penetrated into either one ofthe first and the second magnetic shield layers 60 a, 60 b, it tends toflow inside such magnetic shield layer. Subsequently, even if magneticflux may get out of the magnetic shield layer, it tends to penetrateinto another magnetic shield layer. In other words, in such MRAM device10, a magnetic path is secured by the first and the second magneticshield layers 60 a, 60 b. Accordingly, in the MRAM device 10,penetration of magnetic flux into the TMR device section 40 whereinformation is recorded and held is effectively suppressed.

Now, a method of forming the magnetic shield layer of the MRAM device 10as constructed hereinabove will be described.

The first and the second magnetic shield layers 60 a, 60 b of the nanogranular structure may be formed in accordance with a regular nanogranular forming technique. For example, a sputtering is carried out onthe surface where the nano granular film is formed by using a(Cu_(0.92)Fe_(0.08))₉₀Al₁₀ target, thereby forming an FeCo—Al—O nanogranular film comprising a non-magnetic layer of Al₂O₃ at the grainboundary of an FeCo layer which is a magnetic layer (See Journal ofInstitute of Applied Magnetic of Japan No. 25, pp 871-874, 2001). Otherthan the above mentioned Fe—Al—O nano granular film, the nano granularfilm may be any nano granular film having a composition of Fe—Al—O,Co—Al—O or the like.

Also, the high permeability soft magnetic metal to be used for the firstand the second magnetic shield layers 60 a, 60 b may be, for example,Fe, FeCo, FeSi, FeSiAl, FeAl or NiFe. Even in case of forming the nanogranular film using such materials, it is possible to film form by thesputtering technique as is the case of forming the nano granular film.

In case of making the MRAM device 10 provided with the first and thesecond magnetic shield layers 60 a, 60 b which are formed in the manneras described hereinabove, for example, the transistor section 20 isfirst formed on a wafer constituting the silicon substrate 21 through anormal processing before being placed in a sputtering chamber.Subsequently, the word line 30, many layers comprising the TMR devicesection 40 and the bit line 50 are sequentially film formed inlamination by the sputtering technique. The first magnetic shield layer60 a and the second magnetic shield layer 60 b are formed respectivelyon the bottom surface of the transistor section 20 and on the topsurface of the bit line 50 by the sputtering technique using the targetwhich has been described hereinabove as an example.

After forming the second magnetic shield layer 60 b, a passivation film70 is formed thereon. Subsequently, necessary processes such as makingholes in the passivation film 70 and the second magnetic shield layer 60b for forming pads on the passivation film 70 are carried out beforedicing, thereby forming discrete MRAM devices 10 each covered with thepassivation film 70 on the top surface.

Other than the above example, the MRAM device 10 may be made, forexample, by forming the first magnetic shield layer 60 a on the bottomsurface of the silicon substrate 21 prior to forming the TMR devicesection 40. Then, it is placed in a sputtering chamber to form only thesecond magnetic shield layer 60 b after forming the bit line 50. In thiscase, the first magnetic shield layer 60 a which is formed in advancecan be formed by any film forming technique other than the sputtering.

Moreover, the MRAM device 10 may be formed, for example, by placing asemi-completed product having the transistor section 20, the word line30, the respective layers constituting the TMR device section 40 and thebit line 50 through appropriate processing, thereby forming the firstand the second magnetic shield layers 60 a, 60 b by the sputteringtechnique. It is to be noted in this case that the first magnetic shieldlayer 60 a may be formed in advance by any technique other than thesputtering and forming only the second magnetic shield layer 60 b by thesputtering technique.

As shown in the above examples, in fabricating the MRAM device 10, thefirst and the second magnetic shield layers 60 a, 60 b may be formed bythe sputtering technique. And what is important herein is that thecomposing elements of the targets which are used in forming the softmagnetic layers constituting the first and the second magnetic shieldlayers 60 a, 60 b are common to a part of the elements of the target tobe used for forming various layers of the MRAM device 10.

In other words, targets such as Fe, Co, Pt, Mn, Al and the like forforming the TMR device section 40 and the targets for forming the firstand the second magnetic shield layers 60 a, 60 b may be provided in asingle sputtering chamber, thereby enabling to form the various layersin a common chamber. This means that any possibility of introducingimpurities that may adversely affect the storage and holdingcharacteristic of the MRAM device 10 can be suppressed at the time offorming the MRAM device 10 having the first and the second magneticshield layers 60 a, 60 b. Additionally, it helps to cut production costand improves production yield.

It is to be noted that the first and the second magnetic shield layers60 a, 60 b may be made by various conventional film forming techniquessuch as a plating technique, a spin coating technique or the like otherthan the above mentioned sputtering technique. Moreover, an aerosoldeposition (AD) technique in which fine particles of raw materialscomposing of a film are made in aerosol and are bombarded onto an objecton which the film is formed can be used for forming the first and thesecond magnetic shield layers 60 a, 60 b because it is useful for easilyforming a thick film at a high speed.

Furthermore, as described hereinabove, it is possible to form the firstand the second magnetic shield layers 60 a, 60 b by using different filmforming techniques from each other. For example, the first magneticshield layer 60 a is film formed on the bottom surface of the siliconsubstrate 21 by the spin coat technique, while the second magneticshield layer 60 b is film formed on the top surface of the bit line 50by the sputtering technique. At the time of choosing each film formingtechnique, it is necessary to consider productivity of the MRAM device10, film thickness of the magnetic shield layer to be formed and thelike.

Now, the magnetic shielding characteristic by the magnetic shield layerwill be described.

An evaluation of the magnetic shielding characteristic is made on themagnetic shield layer made from a soft magnetic layer of the nanogranular structure with the composition of Fe—Al—O. The Fe—Al—O nanogranular film is formed by firstly sputtering Fe and Al and then makingthe sputtering chamber an oxidation atmosphere to allow naturaloxidation. It is to be noted at the time of characteristic evaluationthat measurements of saturation magnetization and anisotropic magneticfield are made by film forming Fe—Al—O on separate substrates whileapplying a magnetic field.

The saturated magnetization of the formed nano granular film was 1.1T,the coercive force was 2.3 A/m and anisotropic magnetic field was 6kA/m. Permeability was μ′=200 and μ″=20 (both at 100 MHz) and tendencywas seen that loss becomes higher at high frequency.

Additionally, MRAM devices having the magnetic shield layers and MRAMdevices having no magnetic shield layers are fabricated. Externalmagnetic fields are applied to these MRAM devices to measure strength ofmagnetic field inside the MRAM device. Measurements were made byexternally applying 200 Oe magnetic field onto the MRAM devices havingthe magnetic shield layer up to 200 nm.

FIG. 2 is a graph to show the relationship between the film thickness ofthe magnetic shield layer of the MRAM device and the strength ofmagnetic field inside the device. In FIG. 2, the horizontal axisrepresents the film thickness (nm) of the magnetic shield layer, whilethe vertical axis represent the strength of magnetic field (Oe) insidethe device.

As shown in FIG. 2, strength of the internal magnetic field due toapplication of 200 Oe external magnetic field onto the MRAM devicedecreases as the film thickness of the magnetic shield layer increases.In general, the inverting magnetic field of the MRAM device is about 30Oe. Judging from the result as shown in FIG. 2, the magnetic shieldlayer is required to be as thick as about 170 nm in order to reduce theexternal magnetic field less than the above value. However, since theoptimum film thickness of the magnetic shield layer depends on themagnetic environment at the location where the MRAM device is disposedand the material of the magnetic shield layer, the measurement resultsdo not mean that all MRAM devices should have the film thickness equalto about 170 nm. The relationship in FIG. 2 shows that the internalmagnetic field can be adjusted by varying the film thickness of themagnetic shield layer. It is therefore possible that the film thicknesscan be set in response to the magnetic environment of the MRAM device.

As described hereinabove, in consideration of problems associated withconventional technique such as difficulties in both fabricationfacilities and performance of forming the ferrite layer after formationof the MRAM device using a single sputtering chamber and relatively lowpermeability of the ferrite layer as compared with a soft magnetic metaleven if it is formed, the present invention features in forming amagnetic shield layer using soft magnetic metal.

The magnetic shield layer of soft magnetic metal may be formed to havethe nano granular structure or may be made from soft magnetic metalhaving high permeability. Since soft magnetic layers are chosen to havepartly common composing elements to elements of the targets to be usedfor forming various layers of the MRAM device, a common sputteringchamber that is used for forming the layers of the MRAM device can beused for forming the soft magnetic layer. Accordingly, the MRAM deviceprovided with magnetic shield layers can be fabricated efficiently andthe fabrication steps can be suppressed to the minimum, thereby reducingthe fabrication cost.

The MRAM device provided with the magnetic shield layers as formed inthe above manner is able to suppress the magnetic flux penetrating fromthe external magnetic fields down to a level below the invertingmagnetic field strength of the recording layer, improve storage and holdstability and enable to be used under sever magnetic field environment.

Moreover, the aforementioned MRAM device 10 may be designed to have aconstruction in which both of the first and the second magnetic shieldlayers 60 a, 60 b formed on the bottom and top surfaces of the MRAMdevice 10 are magnetically coupled together. FIG. 3 is a simplifieddrawing to show an exemplified construction of the MRAM device in whichthe magnetic shield layers are coupled together. It is to be noted inFIG. 3 that constituent elements equivalent to those in FIG. 1 use thesame reference numerals and their detailed descriptions are omitted.

The MRAM device 10 is provided with the first and the second magneticshield layers 60 a, 60 b on the top and the bottom surfaces thereof,respectively. The MRAM device 10 is mounted on a lead frame 80 at theside of the first magnetic shield layer 60 a and is provided with thepassivation film 70 on the second magnetic shield layer 60 b. The MRAMdevice 10 is also formed with a third magnetic shield layer 60 c on theside surface. The third magnetic shield layer 60 c is designed tomagnetically couple the first and the second magnetic shield layers 60a, 60 b.

In the MRAM device 10 provided with such magnetic shielding structure, amagnetic path is formed through the first, the second and the thirdmagnetic shield layers 60 a, 60 b and 60 c. Accordingly, magnetic fluxfrom external magnetic fields do not penetrate inside the MRAM device10, rather conducted to the first, the second and the third magneticshield layers 60 a, 60 b and 60 c, thereby suppressing penetration intothe device. Furthermore, the magnetic flux once entered into either oneof the first, the second and the third magnetic shield layers 60 a, 60 band 60 c tends to be prevented from leaking out of the end of suchmagnetic shield layer or tends to flow into adjacent magnetic shieldlayer, thereby effectively shielding the MRAM device 10 from theexternal magnetic fields.

The third magnetic shield layer 60 c is formed with a soft magneticlayer in the same manner as the first and the second magnetic shieldlayers 60 a, 60 b. A sputtering technique, a plating technique, a spincoat technique, an AD technique or the like may be used for forming thethird magnetic shield layer 60 c. The choice of the techniques forforming the third magnetic shield layer 60 c is made in consideration ofthe construction and productivity of the device on which the thirdmagnetic shield layer 60 c is to be formed, film thickness of the thirdmagnetic shield layer 60 c to be formed, or the like.

It is to be noted that the third magnetic shield layer 60 c may beformed on one side surface of the MRAM device 10 as shown in FIG. 3.However, the magnetic shield layer is preferably formed so as to coverthe entire circumference of the MRAM device 10 for assured suppressionof penetration of the magnetic flux.

It is also possible that the lead frame 80 has integral protrusions ofsoft magnetic member or protrusions each covered with soft magneticmaterial on the surface thereof for locating the MRAM device 10 thereat.FIG. 4 is a simplified drawing to show another exemplified constructionof the MRAM device in which the magnetic shield layers are magneticallycoupled together. However, it is to be noted that the constitutingelements equivalent to those in FIG. 3 have the same reference numeralsand their detailed descriptions are omitted herein.

As shown in FIG. 4, the MRAM device 10 provided with the first and thesecond magnetic shield layers 60 a, 60 b is mounted on the lead frame 80having an integral protrusion 81 made from a soft magnetic material orcovered with a soft magnetic material on the surface thereof. Theprotrusion 81 is formed to extend in the vertical direction with respectto the lead frame 80 in such a manner to be located on the side surfaceof the MRAM device 10 that is mounted on the lead frame 80. Whenmounting the MRAM device 10 on the lead frame 80, end portions of thefirst and the second magnetic shield layers 60 a, 60 b are made incontact with the protrusion 81 or are in the close proximity to it.

It is to be understood that such protrusion 81 is able to provide thesimilar advantages to the third magnetic shield layer 60 c as shown inFIG. 3 and effectively provides magnetic shielding of the MRAM device 10from external magnetic fields. It is also possible to surely suppresspenetration of magnetic flux if the protrusion 81 is formed so as toenclose the MRAM device 10.

Although the first and the second magnetic shield layers defining thesoft magnetic layers are formed at the two locations, i.e., on thedevice mounting surface and the opposite surface of the MRAM device 10in the above description, it is of course possible to form on only thedevice mounting surface or the opposite surface to the device mountingsurface in order to obtain a certain magnetic shielding of magneticfields in a given frequency range.

As described hereinabove, according to the present invention, themagnetic shield layer is formed on the surface of the MRAM device byusing soft magnetic metal. By this construction, penetration of magneticflux inside the MRAM device is suppressed. Accordingly, even if externalmagnetic fields are applied, the magnetic flux penetrated into therecording layer is suppressed below the inversion strength of magneticfield of the recording layer, thereby improving stability of the storageand hold of the information and realizing MRAM devices which can be usedunder severe magnetic field environment.

Moreover, by using soft magnetic metal as the magnetic shield layer, themagnetic shield layer can be formed by the sputtering technique,particularly composing elements can be partly shared as elements of thetargets to be used for forming various layers composing the MRAM deviceby the sputtering technique, thereby enabling to form various layers ofthe MRAM device in a single sputtering chamber. As a result, the MRAMdevice can be fabricated efficiently and can reduce the production cost.

1. A magnetic non-volatile memory device provided with a magneticshielding structure for suppressing the influence of external magneticfields, said device characterized by comprising in that: a magneticshield layer made from a soft magnetic metal is formed on a surface ofsaid device for suppressing penetration of magnetic flux into saiddevice, and said magnetic shield layers are formed on a device surfaceat the mounting side of said device, and on a device surface opposite tosaid mounting side of said device.
 2. (canceled)
 3. The magneticnon-volatile memory device according to claim 1, said devicecharacterized in that: said magnetic shield layer is formed of a nanogranular structure having a magnetic layer and a non-magnetic layer. 4.The magnetic non-volatile memory device according to claim 1, saiddevice characterized in that: said magnetic shield layer has a composingelement which is common to a part of an element of various layerscomposing said device.
 5. The magnetic non-volatile memory deviceaccording to claim 1, said device characterized in that: a passivationfilm is formed on said magnetic shield layer.
 6. The magneticnon-volatile memory device according to claim 1, said devicecharacterized in that: said magnetic shield layers formed on a devicesurface at the mounting side of said device, and a device surfaceopposite to said mounting side of said device, are magnetically coupledwith each other.
 7. The magnetic non-volatile memory device according toclaim 4, said device characterized in that: said composing elementincludes one selected from the group consisting of Fe, Co, Pt, Mn, andAl.
 8. A method for manufacturing a magnetic non-volatile memory deviceprovided with a magnetic shielding structure for suppressing theinfluence of external magnetic fields, said method characterized inthat: various layers formed in said device, and a magnetic shield layerformed on a surface of said device for suppressing penetration ofmagnetic flux into said device are formed in a single sputteringchamber.